JP60-37455A discloses a continuously variable transmission in which a two-forward speed subtransmission mechanism is provided in series with a continuously variable speed change mechanism (to be referred to hereafter as a “variator”), and a gear position of the subtransmission mechanism is changed in accordance with an operating condition of a vehicle. Thus, an achievable speed ratio range is enlarged without increasing the size of the variator.
JP5-79554A discloses control (to be referred to hereafter as a “coordinated shift”) employed in this type of continuously variable transmission including a subtransmission mechanism which varies a speed ratio of the variator in an opposite direction to a speed ratio variation direction of the subtransmission mechanism in accordance with change of the gear position of the subtransmission mechanism. When this coordinated shift is performed, speed variation occurring in an engine and a torque converter during a shift in the subtransmission mechanism is suppressed, thereby preventing shift shock caused by inertia torque from the engine and torque converter.